Berlin 2008 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 32: Correlated Electrons: Poster Session

TT 32.12: Poster

Donnerstag, 28. Februar 2008, 14:00–18:00, Poster B

Dynamic magnetic order in CeCu₂Si₂ — •O. Stockert¹, J. Arndt¹, E. Faulhaber², H.S. Jeevan¹, C. Geibel¹, P. Fouquet³, and F. Steglich¹ — ¹Max-Planck-Institut CPfS, Dresden, Germany — ²Institut für Festkörperphysik, TU Dresden, Dresden, Germany — ³Institut Laue-Langevin, Grenoble, France

The heavy-fermion compound CeCu₂Si₂ attracts still considerable interest due to the competition between antiferromagnetic order and superconductivity. The nature of the magnetic order is an incommensurate spin-density wave below T_N ≈ 800 mK determined by the nesting properties of the Fermi surface. Recently we observed that the magnetic Bragg peaks in only magnetically ordered CeCu₂Si₂ are broadened in q space. Starting from long-range order the magnetic Bragg peaks broaden below T ≈ 550 mK. At T = 100 mK a correlation length ξ ≈ 130 Å has been estimated. From this finite correlation length/domain size at lowest temperature a finite lifetime of the magnetic peaks was expected. However, in neutron scattering experiments using a triple-axis spectrometer no broadening in energy was observed. Hence, the neutron spin-echo technique was chosen for this investigation due to the higher energy resolution. Data were recorded at different temperatures below T_N. From the spin-echo spectra some dynamic nature of the magnetic order in only magnetically ordered CeCu₂Si₂ can be inferred. The fluctuation rate of the antiferromagnetic order is estimated to be in the order of 50 MHz at lowest temperatures. Our results will be discussed in comparison to other measurements.